Method and apparatus for improving sidewall coverage during sputtering in a chamber having an inductively coupled plasma

ABSTRACT

Increased sidewall coverage by a sputtered material is achieved by generating an ionizing plasma in a relatively low pressure sputtering gas. By reducing the pressure of the sputtering gas, it is believed that the ionization rate of the deposition material passing through the plasma is correspondingly reduced which in turn is believed to increase the sidewall coverage by the underlayer. Although the ionization rate is decreased, sufficient bottom coverage of the by the material is maintained. In an alternative embodiment, increased sidewall coverage by the material may be achieved even in a high density plasma chamber by generating the high density plasma only during an initial portion of the material deposition. Once good bottom coverage has been achieved, the RF power to the coil generating the high density plasma may be turned off entirely and the remainder of the deposition conducted without the high density plasma. Consequently, it has been found that good sidewall coverage is achieved in the latter part of the deposition.

FIELD OF THE INVENTION

[0001] The present invention relates to plasma generators, and moreparticularly, to a method and apparatus for generating a plasma tosputter deposit a layer of material in the fabrication of semiconductordevices.

BACKGROUND OF THE INVENTION

[0002] Low pressure radio frequency (RF) generated plasmas have becomeconvenient sources of energetic ions and activated atoms which can beemployed in a variety of semiconductor device fabrication processesincluding surface treatments, depositions, and etching processes. Forexample, to deposit materials onto a semiconductor wafer using a sputterdeposition process, a plasma is produced in the vicinity of a sputtertarget material which is negatively biased. Ions created adjacent thetarget impact the surface of the target to dislodge, i.e., “sputter”material from the target. The sputtered materials are then transportedand deposited on the surface of the semiconductor wafer.

[0003] Sputtered material has a tendency to travel in straight linepaths, from the target to the substrate being deposited, at angles whichare oblique to the surface of the substrate. As a consequence, materialsdeposited in etched openings including trenches and holes ofsemiconductor devices having openings with a high depth to width aspectratio, may not adequately coat the walls of the openings, particularlythe bottom walls. If a large amount of material is being deposited, thedeposited material can bridge over causing undesirable cavities in thedeposition layer. To prevent such cavities, sputtered material can beredirected into substantially vertical paths between the target and thesubstrate by negatively biasing (or self biasing) the substrate andpositioning appropriate vertically oriented electric fields adjacent thesubstrate if the sputtered material is sufficiently ionized by theplasma. However, material sputtered by a low density plasma often has anionization degree of less than 10% which is usually insufficient toavoid the formation of an excessive number of cavities. Accordingly, itis desirable to increase the density of the plasma to increase theionization rate of the sputtered material in order to decrease theformation of unwanted cavities in the deposition layer. As used herein,the term “dense plasma” is intended to refer to one that has a highelectron and ion density, in the range of 10¹¹-10¹³ ions/cm³.

[0004] There are several known techniques for exciting a plasma with RFfields including capacitive coupling, inductive coupling and waveheating. In a standard inductively coupled plasma (ICP) generator, RFcurrent passing through a coil surrounding the plasma induceselectromagnetic currents in the plasma. These currents heat theconducting plasma by ohmic heating, so that it is sustained in steadystate. As shown in U.S. Pat. No. 4,362,632, for example, current througha coil is supplied by an RF generator coupled to the coil through animpedance matching network, such that the coil acts as the firstwindings of a transformer. The plasma acts as a single turn secondwinding of a transformer.

[0005] Although such techniques can reduce the formation of voids,further reduction of void formation is needed.

SUMMARY OF THE PREFERRED EMBODIMENTS

[0006] It is an object of the present invention to provide an improvedmethod and apparatus for generating a plasma within a chamber and forsputter depositing a layer which enhances both sidewall and bottomcoverage.

[0007] These and other objects and advantages are achieved by, inaccordance with one aspect of the invention, a plasma generatingapparatus in which a layer of titanium, a titanium compound or othersuitable deposition material is deposited in such a manner as toincrease the coverage of sidewalls of channels, vias and other highaspect ratio openings and structures having a sidewall in a substrate.It has been found that by increasing the sidewall coverage ofunderlayers, the flow of aluminum or other overlayer materials into theopening is enhanced so as to substantially reduce the formation of voidsin the overlayer.

[0008] In one embodiment, increased sidewall coverage by an underlayermaterial is achieved by generating an ionizing plasma in a relativelylow pressure precursor or sputtering gas. By reducing the pressure ofthe sputtering gas, it is believed that the ionization rate (or thedirectionality or both) of the underlayer deposition material passingthrough the plasma is correspondingly reduced which in turn is believedto increase the sidewall coverage by the underlayer. Although theionization rate is decreased, sufficient bottom coverage of the channelsby the underlayer material is maintained. Another advantage of reducingthe sputtering gas pressure is that the deposition rate of theunderlayer material may be increased as well.

[0009] In an alternative embodiment, increased sidewall coverage by theunderlayer material may be achieved even in a high density plasmachamber by generating the high density plasma only during an initialportion of the underlayer material deposition. It has been found thatgood bottom coverage may be achieved by ionizing the underlayerdeposition material using a high density plasma during the initialportion of the deposition. Once good bottom coverage has been achieved,the RF power to the coil generating the high density plasma may beturned off entirely and the remainder of the underlayer depositionconducted without the high density plasma. It has been found that goodsidewall coverage is then achieved in the latter part of the deposition.Consequently, good overall coverage of the opening is achieved combiningthe bottom coverage of the initial portion of the deposition with thesidewall coverage obtained during the latter portion of the underlayerdeposition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective, partial cross-sectional view of a plasmagenerating chamber for improving sidewall coverage in a manner inaccordance with an embodiment of the present invention.

[0011]FIG. 2 is a schematic diagram of the electrical interconnectionsto the plasma generating chamber of FIG. 1.

[0012]FIG. 3 is a cross-sectional view of an opening having anunderlayer of deposition material deposited in a high density plasma.

[0013]FIG. 4 is a cross-sectional view of the opening of FIG. 3 havingan interconnect layer deposited over the underlayer of FIG. 3.

[0014]FIG. 5(a) is a cross-sectional view of an opening deposited withan underlayer of deposition material in a low pressure plasma inaccordance with the present invention.

[0015]FIG. 5(b) is a cross-sectional view of the opening of FIG. 5(a)having an interconnect layer deposited over the underlayer of FIG. 5(a).

[0016]FIG. 6 is a schematic top plan view of a staged-vacuum, multiplechamber semiconductor wafer processing system incorporating the vacuumchamber of FIGS. 1-2.

DETAILED DESCRIPTION OF THE DRAWINGS

[0017] Referring first to FIGS. 1-2, an example of a plasma generatorused in accordance with an embodiment of the present invention comprisesa substantially cylindrical plasma chamber 100 which is received in avacuum chamber 102 (FIG. 2). The plasma chamber 100 of this embodimenthas a single helical coil 104 which is carried internally of the vacuumchamber walls by a chamber shield 106. The chamber shield 106 protectsthe interior walls of the vacuum chamber 102 from the material beingdeposited within the interior of the plasma chamber 100.

[0018] Radio frequency (RF) energy from an RF generator 300 (FIG. 2) isradiated from the coil 104 into the interior of the plasma chamber 100,which energizes a plasma within the plasma chamber 100. An ion fluxstrikes a negatively biased target 110 positioned above the plasmachamber 100. The plasma ions eject material from the target 110 onto asubstrate 112 which may be a wafer or other workpiece supported by apedestal 114 at the bottom of the plasma chamber 100. An optionalrotating magnet assembly 116 may be provided above the target 110 toproduce magnetic fields which sweep over the face of the target 110 topromote uniform erosion by sputtering of the target 110.

[0019] The deposition material sputtered from the target 110 passesthrough the plasma energized by the coil 104 prior to being deposited onthe substrate 112. A portion of the deposition material passing thoughthe plasma is ionized by the plasma. The ionized deposition material isthen attracted to a negative potential on the substrate 112. In thismanner, the ionized deposition material is redirected to a more verticalpath which facilitates depositing more material into high aspect ratioopenings in the substrate.

[0020] As will be explained in greater detail below, in accordance withone aspect of the present invention, the ionization of the depositionmaterial is controlled so as to improve the sidewall coverage ofopenings or other structures having sidewalls while maintaining goodbottom coverage as well. Such an arrangement is particularly useful whendepositing an underlayer for an interconnect layer of a metal such asaluminum. For example, the improved sidewall coverage of the underlayerhas been found to significantly facilitate the flow of aluminum into thechannel, even when the aluminum is not ionized, so as to significantlyreduce the incidence of undesirable voids forming in the aluminum layer.

[0021] A deposition process in accordance with the present invention isuseful for a variety of underlayers including wetting layers, seedlayers, nucleation layers and barrier layers formed from a variety ofdeposition materials including aluminum, copper, tungsten, tungstenfluoride, titanium, titanium nitride and tantalum nitride. In addition,any structure having a sidewall can benefit this process includingcapacitor electrodes formed of a number of electrode materials includingtitanium and platinum. The process may be used to deposit ferroelectricsincluding BST (barium strontium titanate) and PZT (lead zirconiumtitanate) and conductors including aluminum, copper and gold.

[0022]FIG. 2 includes a schematic representation of the electricalconnections of the plasma generating apparatus of this illustratedembodiment. To sputter target material onto the substrate 112, thetarget 110 is preferably negatively biased by a variable DC power source302 to attract the ions generated by the plasma. In the same manner, thepedestal 114 may be negatively biased by a variable DC power source 304to bias the substrate 112 negatively to attract the ionized depositionmaterial to the substrate 112. In an alternative embodiment, thepedestal 114 may be biased by a high frequency RF power source to biasthe substrate 112 so as to attract the ionized deposition material moreuniformly to the substrate 112. In yet another alternative embodiment,as set forth in copending application Ser. No. 08/677,588, entitled “AMethod for Providing Full-face High Density Plasma Physical VaporDeposition,” filed Jul. 9, 1996 (Attorney Docket # 1402/PVD/DV) andassigned to the assignee of the present application, an external biasingof the substrate 112 may be omitted.

[0023] One end of the coil 104 is coupled to an RF source such as theoutput of an amplifier and matching network 306, the input of which iscoupled to the RF generator 300. The other end of the coil 104 iscoupled to ground, preferably through a capacitor 308, which may be avariable capacitor.

[0024] The coil 104 is carried on the chamber shield 106 by a pluralityof coil standoffs 120 (FIG. 1) which electrically insulate the coil 104from the supporting chamber shield 106. In addition, the insulating coilstandoffs 120 have an internal labyrinth structure which permitsrepeated deposition of conductive materials from the target 110 onto thecoil standoffs 120 while preventing the formation of a completeconducting path of deposited material from the coil 104 to the chambershield 106. Such a completed conducting path is undesirable because itcould short the coil 104 to the chamber shield 106 (which is typicallygrounded).

[0025] RF power is applied to the coil 104 by feedthrough bolts whichare supported by insulating feedthrough standoffs 124. The feedthroughstandoffs 124, like the coil support standoffs 120, permit repeateddeposition of conductive material from the target onto the feedthroughstandoff 124 without the formation of a conducting path which couldshort the coil 104 to the chamber shield 106. The coil feedthroughstandoff 124, like the coil support standoff 120, has an internallabyrinth structure to prevent the formation of a short between the coil104 and the wall 126 of the shield. The feedthrough is coupled to the RFgenerator 300 (shown schematically in FIG. 2) through the matchingnetwork 306 (also shown schematically in FIG. 2).

[0026] As set forth above, the RF power radiated by the coil 104energizes the plasma in the chamber to ionize the target material beingsputtered from the target 110. The ionized sputtered target material isin turn attracted to the substrate 112 which is at a negative (DC or RF)potential to attract the ionized deposition material to the substrate112.

[0027]FIG. 3 shows in cross section an opening 400 in an oxide layer 402of a substrate in which an underlayer 404 of titanium has beendeposited. The opening 400 may be a via, channel or other structurehaving a sidewall or a narrow cross-sectional width (1 micron or less,for example) and a high depth to width aspect ratio. In the example ofFIG. 4, the opening has a width of approximately 0.34 microns and adepth to width aspect ratio of approximately 3. Absent ionization, muchof the titanium atoms arriving on the surface 406 of the substrate wouldbe at angles too oblique to penetrate very deeply into the opening 400.Consequently, to increase the amount of material entering the opening400, titanium sputtered from the target 110 is preferably ionized by theplasma in the chamber so that the path of travel of at least some of thedeposition material is more vertically aligned so as to reach the bottomof the opening 400.

[0028] In the deposition of the titanium underlayer 404 of FIG. 4, thepressure of the argon precursor or sputtering gas was approximately 30mTorr, a typical value for high density plasma sputtering. Although theionization of the titanium at this pressure permits very good bottomcoverage as indicated by the bottom portion 408 of the underlayer 404,it has been found that the resultant sidewall coverage can be very thinas indicated by the side wall portion 410 of the underlayer 404, or evendiscontinuous. It is believed that sidewall coverage this thin hindersthe interaction between the titanium underlayer 404 and the subsequentlydeposited aluminum interconnect layer 412 (FIG. 4) such that voids 414form in the aluminum layer at an undesirable rate.

[0029] It has been found that the sidewall coverage of the underlayermay be significantly improved by generating the ionizing plasma at apressure substantially below the pressures typically used in highdensity plasma sputterings. FIG. 5(a) shows an opening 500 in an oxidelayer 502 of a substrate in which an underlayer 504 of titanium has beendeposited in a plasma generated at an argon sputtering gas pressure of 5mTorr rather than 30 mTorr. As shown in FIG. 5(a), very good bottomcoverage as indicated by the bottom portion 508 has been maintained yetthe sidewall coverage has been substantially thickened as indicated bythe side wall portion 510 of the underlayer 504. (The relativeproportions of the underlayer 504 are not shown to scale in FIG. 5(a)but are exaggerated for purposes of clarity.) This improved sidewallcoverage is believed to result from a decrease in the ionization rate ofthe titanium by the plasma. Because the plasma is generated in a lowerpressure argon sputtering gas, it is believed that fewer argon ions andelectrons are generated in the plasma such than fewer atoms of thetitanium are ionized prior to depositing on the substrate. As aconsequence, the angle of incidence of the titanium atoms is, onaverage, more oblique such that an increased percentage of the titaniumis deposited on the sidewall rather than the bottom of the opening 500.Nonetheless, a sufficient amount of the titanium is ionized so as toensure adequate bottom coverage of the opening 500 as well. It isbelieved that both good sidewall and good bottom coverages may beachieved at other sputtering gas pressures below 30 mTorr including 20and 10 mTorr.

[0030]FIG. 5(b) shows an aluminum interconnect layer 512 deposited ontothe titanium underlayer 504. Because of the improved sidewall coverageof the underlayer 504, the aluminum interaction with the titaniumunderlayer 504 is improved such that the opening more frequently fillscompletely without forming a void. Resistances of aluminum interconnectlayers deposited in vias of test wafers in which the underlying titaniumlayers were deposited at pressures of 10 mTorr and 20 mTorr have shownremarkable decreases over those in which the underlying titanium layerswere deposited at 30 mTorr. It is believed that the substantialimprovement in resistance is a result of a substantial reduction in thenumber of voids in the aluminum layer in the vias as a result ofimproved sidewall coverage by the titanium underlayer.

[0031] Although the improved process of the illustrated embodiment hasbeen described in connection with a titanium underlayer and an aluminumoverlayer, it should be appreciated that the present invention isapplicable to enhancing sidewall coverage of wetting layers, seed layersand nucleation layers of other types of materials. For example, theprocess may be applied to enhance the sidewall coverage of under layersformed of titanium nitride, tantalum and tantalum nitride for aluminumfill and copper barrier layers. Other applications include enhancing thesidewalls of seed layers of aluminum or copper for subsequentdepositions of nonionized aluminum or copper, respectively. Still otherexamples include improving sidewall coverage of tungsten nucleationlayers as part of a CVD (chemical vapor deposition) process. Furtherstructures which can benefit from the process of the present inventioninclude electrodes of devices such as capacitors and other conductors.

[0032] In an alternative embodiment, the underlayer for the overlyinginterconnect layer may be formed in a two-step process in which, in thefirst step, an initial portion of the underlayer is deposited in a highpressure (e.g. 30 mTorr) plasma with RF power being applied to the coil104 at a relatively high level such as 1500 watts, for example. As aresult, the initial portion of the underlayer will look substantiallylike the underlayer depicted in FIG. 3 in which good bottom coverage isachieved but the sidewall coverage is relatively thin. However, beforethe deposition of the underlayer is completed, in a second step, the RFpower to the coil 104 may be substantially reduced or even turned off soas to reduce or eliminate ionization of the material being deposited. Asa consequence the amount of deposition material being deposited onto thesubstrate at oblique angles will be increased after the RF power to thecoil is turned off which will in turn enhance the sidewall coverage ofthe openings in a manner similar to that depicted in FIG. 5(a). in thismanner, the bottoms of the openings are preferentially deposited in thefirst step and the sidewalls are preferentially deposited in the secondstep so as to achieve a good overall coating of both the bottoms andsidewalls forming the underlayer. During the second step, the pressuremay be maintained at the full 30 mTorr level or alternatively, sinceionization of the deposition material is reduced or eliminated, thepressure may be reduced substantially so as to reduce scattering andincrease the deposition rate onto the substrate.

[0033]FIG. 6 is a schematic plan view of a staged-vacuum semiconductorwafer processing system 620 of the type which is described in greaterdetail in U.S. Pat. No. 5,186,718. The system 620 includes a housing 622which defines four chambers: a robot buffer chamber 624 at one end, atransfer robot chamber 628 at the opposite end, and a pair ofintermediate processing or treatment chambers 626 and 627. Although oneor more load lock chambers 621 may be used, preferably two or three suchchambers are mounted to the buffer chamber and in communication with theinterior of the buffer robot chamber via access ports 636 and associatedslit valves 638. A plurality of vacuum processing chambers 634(including the chamber 100 described above) are mounted about theperiphery of the transfer robot station. The chambers 634 may be adaptedfor various types of processing including etching and/or deposition.Access is provided to and between each of the chambers by an associatedport 636 and gate valve 638.

[0034] The robot chambers 624 and 628 communicate with one another viathe intermediate processing or treatment chambers 626 and 627 (alsocalled “treatment” chambers). Specifically, intermediate treatmentchamber 626 is located along a corridor or pathway 630 which connectsthe transfer robot chamber 628 to the buffer robot chamber 624.Similarly, the second intermediate treatment chamber 627 is locatedalong a separate corridor or pathway 632 which connects the robots 628and 624. These separate paths between the two robot or transfer chamberspermit one path to be used for loading or unloading while the system isbeing used for wafer processing treatment and, thus, provide increasedthroughput. The chambers 626 and 627 can be dedicated to pre-treating(e.g., plasma etch cleaning and/or heating) of the wafers beforeprocessing in chambers 634 or post-treating (e.g., cool-down) of thewafers following treatment in chambers 634; alternatively, one or bothof the chambers 626 and 627 can be adapted for both pre-treatment andpost-treatment.

[0035] Preferably, the housing 622 is a monolith, i.e., it is machinedor otherwise fabricated of one piece of material such as aluminum toform the four chamber cavities 624, 626, 627 and 628 and theinterconnecting corridors or pathways 630 and 632. The use of themonolith construction facilitates alignment of the individual chambersfor wafer transport and also eliminates difficulties in sealing theindividual chambers.

[0036] One typical operational cycle of wafer transport through thesystem 20 is as follows. Initially, an R THETA buffer robot 640 inchamber 624 picks up a wafer from a cassette load lock 621 andtransports the wafer to chamber 626 which illustratively etch cleans thesurface of the wafer. R THETA transfer robot 642 in chamber 628 picks upthe wafer from the pre-cleaning chamber 626 and transfers the wafer to aselected one of the preferably high vacuum processing chambers 634. Oneof these chambers is the chamber 100 which deposits an underlayer oftitanium or other suitable material as set forth above. Followingprocessing, transfer robot 642 can transfer the wafer selectively to oneor more of the other chambers 634 for processing. Included amongst thesechambers is a deposition chamber which deposits aluminum or othersuitable interconnect material on the underlayer previously deposited inthe chamber 100. Because the underlayer has good sidewall as well asbottom coverage, the chamber depositing the aluminum may be aconventional magnetron sputtering chamber which does not have an RF coilto produce a high density plasma to ionize the aluminum. Instead, thealuminum may be deposited without being ionized yet can form aninterconnect layer having a relatively low resistance with few or novoids in the openings. Upon completion of depositions and etchings, thetransfer robot 642 transfers the wafer to intermediate processingchamber 627 which illustratively is a cool-down chamber. After thecool-down cycle, buffer robot 640 retrieves the wafer from the chamber627 and returns it to the appropriate cassette load lock chamber 621.

[0037] The buffer robot 640 may be any suitable robot such as the dualfour-bar link robot disclosed in allowed Maydan et. al. patentapplication, entitled “Multi-Chamber Integrated Process System”, U.S.application Ser. No. 283,015, now abandoned, which application isincorporated by reference. The transfer robot 642 likewise may be anysuitable robot such as the robot described in the aforementioned U.S.Pat. No. 5,186,718.

[0038] The control functions described above for the system 600including the control of power to the RF coils, targets and substrates,robot control, chamber venting and pumping control, and cassetteindexing are preferably provided by a workstation (not shown) programmedto control these system elements in accordance with the abovedescription.

[0039] In each of the embodiments discussed above, a multiple turn coil104 was used, but, of course, a single turn coil may be used instead.Still further, instead of the ribbon shape coil 104 illustrated, eachturn of the coil 104 may be implemented with a flat, open-ended annularring as described in copending application Ser. No. 08/680,335, entitled“Coils for Generating a Plasma and for Sputtering,” filed Jul. 10, 1996(Attorney Docket # 1390-CIP/PVD/DV) and assigned to the assignee of thepresent application, which application is incorporated herein byreference in its entirety.

[0040] Each of the embodiments discussed above utilized a single coil inthe plasma chamber. It should be recognized that the present inventionis applicable to plasma chambers having more than one RF powered coil orRF powered shields. For example, the present invention may be applied tomultiple coil chambers for launching helicon waves of the type describedin aforementioned copending application Ser. No. 08/559,345, filed Nov.15, 1995 and entitled “Method And Apparatus For Launching a Helicon Wavein a Plasma” (Atty Docket No. 938).

[0041] The appropriate RF generators and matching circuits arecomponents well known to those skilled in the art. For example, an RFgenerator such as the ENI Genesis series which has the capability to“frequency hunt” for the best frequency match with the matching circuitand antenna is suitable. The frequency of the generator for generatingthe RF power to the coil 104 is preferably 2 MHz but it is anticipatedthat the range can vary from, for example, 1 MHz to 4 MHz. An RF powersetting of 1.5 kW is preferred but a range of 1.5-5 kW is satisfactory.In addition, a DC power setting for biasing the target 110 of 5 kW ispreferred but a range of 2-10 kW and a pedestal 114 bias voltage of −30volts DC is satisfactory.

[0042] A variety of sputtering gases may be utilized to generate theplasma including Ar, H₂, O₂ or reactive gases such as NF₃, CF₄ and manyothers. Various sputtering gas pressures are suitable includingpressures of 0.1-50 mTorr. For ionized PVD, a pressure between 10 and100 mTorr is preferred for best ionization of sputtered material.

[0043] It will, of course, be understood that modifications of thepresent invention, in its various aspects, will be apparent to thoseskilled in the art, some being apparent only after study, others beingmatters of routine mechanical and electronic design. Other embodimentsare also possible, their specific designs depending upon the particularapplication. As such, the scope of the invention should not be limitedby the particular embodiments herein described but should be definedonly by the appended claims and equivalents thereof.

What is claimed is:
 1. A process for sputter depositing a layer ofmaterial into a workpiece structure having a sidewall, comprising:providing a sputtering gas into a chamber at a pressure below 20 mTorr;applying RF power to a coil to ionize the sputtering gas to form aplasma; sputtering a target to sputter target material toward aworkpiece; and ionizing a portion of said sputtered target materialbefore it is deposited onto said workpiece.
 2. The process of claim 1wherein said sputtering gas is at a pressure of 5-10 mTorr.
 3. Theprocess of claim 1 wherein said target material is selected from thegroup of titanium, tantalum, aluminum, copper and tungsten.
 4. Theprocess of claim 3 wherein said target material is a compound ofnitrogen and a material selected from the group of tantalum andtitanium.
 5. A process for sputter depositing a layer of material into avia or channel of a workpiece, comprising: providing a sputtering gasinto a chamber; applying RF power to a coil to ionize the sputtering gasto form a plasma; sputtering a target to sputter target material towarda workpiece; ionizing a portion of said sputtered target material beforeit is deposited onto said workpiece; reducing said RF power to said coilwhile continuing to sputter said target so as to reduce ionization ofsaid sputtered target material before it is deposited onto saidworkpiece.
 6. The process of claim 5 wherein said RF power reducing stepreduces said RF power to zero.
 7. A process for sputter depositing alayer of material into an opening of a workpiece, said opening having abottom and sidewalls, said process comprising: sputtering a target tosputter target material toward a workpiece; ionizing a portion of saidsputtered target material before it is deposited onto said workpiece sothat sputtered material which is deposited in said opening is depositedprimarily on the bottom of said opening; and reducing said ionizing ofsputtered material so that sputtered material deposited in said openingis deposited primarily on the sidewalls of said opening.
 8. The processof claim 7 wherein said ionizing reducing step reduces ionization ofsputtered material to zero.
 9. The process of claim 7 wherein saidsputtering gas is at a pressure of 5-10 mTorr.
 10. The process of claim7 wherein said target material is selected from the group of titanium,tantalum, aluminum, copper and tungsten.
 11. A process for sputterdepositing layers of materials into a workpiece structure having asidewall and a bottom, comprising: sputtering a first target in a firstchamber to sputter target material toward a workpiece; ionizing aportion of said sputtered first target material before it is depositedonto said workpiece so that sputtered material which is deposited onsaid structure is deposited primarily on the bottom of said structure;and reducing said ionizing of said sputtered first target material sothat sputtered first target material deposited on said structure isdeposited primarily on the sidewalls of said structure; transferringsaid workpiece to a second chamber; sputtering a second target tosputter a second target material onto said structure of said workpieceto deposit on top of said first material deposited on said structure.12. The process of claim 11 wherein said sputtering gas is at a pressureof 5-10 mTorr.
 13. The process of claim 11 wherein said first targetmaterial is selected from the group of titanium, tantalum, aluminum,copper and tungsten.
 14. The process of claim 11 wherein said secondtarget material is selected from the group of aluminum and copper.
 15. Aprocess for sputter depositing layers of materials into a via or channelof a workpiece, comprising: providing a sputtering gas into a firstchamber at a pressure below 20 mTorr; applying RF power to a coil insaid first chamber to ionize said sputtering gas to form a plasma;sputtering a target to sputter a first target material toward aworkpiece; ionizing a portion of said sputtered target material beforeit is deposited onto said workpiece; transferring said workpiece to asecond chamber; sputtering a second target to sputter a second targetmaterial toward said workpiece.
 16. The process of claim 15 wherein saidsputtering gas is at a pressure of 5-10 mTorr.
 17. The process of claim15 wherein said first target material is selected from the group oftitanium, tantalum, aluminum, copper and tungsten.
 18. The process ofclaim 15 wherein said second target material is selected from the groupof aluminum and copper.
 19. An apparatus for energizing a plasma withina semiconductor fabrication system to sputter material onto a workpiece,the apparatus comprising: a semiconductor fabrication chamber having aplasma generation area within said chamber and containing a sputteringgas at a pressure less than 25 mTorr; and a coil carried by said chamberand positioned to couple energy into said plasma generation area. 20.The apparatus of claim 19 including a target including is a targetmaterial selected from the group of titanium, tantalum, aluminum, copperand tungsten.
 21. A semiconductor fabrication system for sputteringmultiple layers of materials onto a workpiece, the system comprising: afirst semiconductor fabrication chamber having a plasma generation areawithin said chamber and containing a sputtering gas at a pressure lessthan 25 mTorr; said first chamber having a target of a first targetmaterial which includes a material selected from the group of titanium,tantalum, aluminum, copper and tungsten; a coil carried by said firstchamber and positioned to couple energy into said plasma generation areato ionize said first target material to form an underlayer of said firstmaterial on said workpiece; a second semiconductor fabrication chamber;and said second chamber having a second target of a second targetmaterial which includes a material selected from the group of aluminumand copper, for forming a layer on said underlayer.
 22. An apparatus forenergizing a plasma within a semiconductor fabrication system to sputtermaterial onto a workpiece, the apparatus comprising: a semiconductorfabrication chamber having a plasma generation area within said chamber;a coil carried by said chamber and positioned to couple energy into saidplasma generation area to ionize said material prior to deposition ontosaid workpiece; an RF generator coupled to said coil to provide RF powerto said coil; and control means for controlling said RF generator toprovide power at a high level during an initial portion of a sputterdeposition and to provide power at a reduced level including zero powerin a subsequent portion of said sputter deposition.
 23. The apparatus ofclaim 22 including a target including a material selected from the groupof titanium, tantalum, aluminum, copper and tungsten.
 24. Asemiconductor fabrication system for sputtering multiple layers ofmaterials onto a workpiece, the system comprising: a first semiconductorfabrication chamber having a plasma generation area within said chamberand a target of a first target material which includes a materialselected from the group of titanium, tantalum, aluminum, copper andtungsten; a coil carried by said chamber and positioned to couple energyinto said plasma generation area to ionize said first target materialprior to deposition onto said workpiece; an RF generator coupled to saidcoil to provide RF power to said coil; and control means for controllingsaid RF generator to provide power at a high level during an initialportion of a sputter deposition and to provide power at a reduced levelincluding zero power in a subsequent portion of said sputter deposition;a second semiconductor fabrication chamber; and said second chamberhaving a second target of a second target material which includes is amaterial selected from the group of aluminum and copper, for forming alayer on said underlayer.